Use Emscripten fetch in networkfilemanager

.github/workflows/emscripten.yml

@@ -0,0 +1,43 @@
+name: Emscripten
+
+on:
+  push:
+      paths-ignore:
+          - 'docs/**'
+  pull_request:
+      paths-ignore:
+          - 'docs/**'
+
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.head_ref || github.ref }}
+  cancel-in-progress: true
+
+permissions:
+  contents: read
+
+jobs:
+
+  emscripten:
+    runs-on: ubuntu-latest
+
+    if: "!contains(github.event.head_commit.message, '[ci skip]') && !contains(github.event.head_commit.message, '[skip ci]')"
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v5
+
+      - name: Build docker
+        run: docker build -t proj-emscripten-builder scripts/ci/emscripten/
+
+      - name: Artifacts folder
+        run: mkdir -p "$PWD"/wasm_out
+
+      - name: Run docker
+        run: docker run --rm -v "$PWD":/build/proj_src -v "$PWD"/wasm_out:/usr/local/wasm proj-emscripten-builder
+
+      - name: Upload artifacts
+        uses: actions/upload-artifact@v4
+        with:
+          name: proj-js-wasm
+          retention-days: 15
+          path: wasm_out/projModule.*

CMakeLists.txt

@@ -282,6 +282,16 @@ if(ENABLE_CURL)
   endif()
 endif()
 
+################################################################################
+# Check for Emscripten fetch
+################################################################################
+
+option(ENABLE_EMSCRIPTEN_FETCH "Enable Emscripten fetch support" OFF)
+set(EMSCRIPTEN_FETCH_ENABLED FALSE)
+if(ENABLE_EMSCRIPTEN_FETCH)
+  set(EMSCRIPTEN_FETCH_ENABLED TRUE)
+endif()
+
 ################################################################################
 
 option(EMBED_PROJ_DATA_PATH "Whether the PROJ_DATA_PATH should be embedded" ON)
@@ -365,7 +375,7 @@ endif()
 
 include(CheckCSourceCompiles)
 function (is_sharp_embed_available res)
-    if (CMAKE_VERSION VERSION_GREATER_EQUAL 3.21 AND
+    if (NOT EMSCRIPTEN AND CMAKE_VERSION VERSION_GREATER_EQUAL 3.21 AND
         ((CMAKE_C_COMPILER_ID STREQUAL "GNU" AND CMAKE_C_COMPILER_VERSION VERSION_GREATER_EQUAL 15.0) OR
          (CMAKE_C_COMPILER_ID STREQUAL "Clang" AND CMAKE_C_COMPILER_VERSION VERSION_GREATER_EQUAL 19.0)))
         # CMAKE_C_STANDARD=23 only supported since CMake 3.21

docs/source/install.rst

@@ -483,6 +483,19 @@ All cached entries can be viewed using ``cmake -LAH`` from a build directory.
     Users will also typically want to set EMBED_PROJ_DATA_PATH=OFF if setting
     USE_ONLY_EMBEDDED_RESOURCE_FILES=OFF.
 
+.. _install_emscripten_fetch:
+.. option:: ENABLE_EMSCRIPTEN_FETCH=ON/OFF
+
+    .. versionadded:: 9.8
+
+    When ON, the function emscripten_fetch is used to get files
+    from the network (grid files, etc), in a similar way as with cURL.
+    PROJ is doing synchronous fetch calls, so emscripten must have the `-pthread` flag enabled.
+    In addition to that, it is very recommended to run it in a Web Worker in the browser,
+    to not block the main thread.
+    It is incompatible with cURL, so ``ENABLE_CURL`` must be OFF.
+    Default: OFF.
+
 
 Building on Windows with vcpkg and Visual Studio 2017 or 2019
 --------------------------------------------------------------------------------

docs/source/spelling_wordlist.txt

@@ -286,6 +286,7 @@ eg
 egm
 ellps
 emphasize
+emscripten
 encodings
 endian
 engsager

docs/source/usage/network.rst

@@ -45,6 +45,12 @@ Authorizing network access can be done in multiple ways:
     with :cpp:func:`proj_context_set_network_callbacks`. Enabling network use
     must still be done with one of the above mentioned method.
 
+Emscripten
+^^^^^^^^^^
+
+To compile with emscripten (to produce a WASM file) with network capability,
+the CMake configure option :ref:`ENABLE_EMSCRIPTEN_FETCH<install_emscripten_fetch>` can be used.
+
 Setting endpoint
 ----------------
 

scripts/ci/emscripten/Dockerfile

@@ -0,0 +1,31 @@
+# Use the official Emscripten SDK image.
+FROM emscripten/emsdk:4.0.5
+
+# Set non-interactive frontend for package installations
+ENV DEBIAN_FRONTEND="noninteractive"
+
+# --- Install System Dependencies ---
+RUN apt-get update && \
+    apt-get install -y \
+    sqlite3 \
+    ninja-build && \
+    # Clean up apt cache to reduce image size
+    rm -rf /var/lib/apt/lists/*
+
+# --- Setup Build Directories ---
+# Define standard locations for building and installing
+ENV BUILD_DIR="/build"
+ENV INSTALL_DIR="/usr/local/wasm"
+
+# Create the directories
+RUN mkdir -p ${BUILD_DIR}/proj_src \
+             ${BUILD_DIR}/deps_src \
+             ${INSTALL_DIR}
+
+# Copy the build script into the container
+COPY build_wasm.sh /scripts/build_wasm.sh
+RUN chmod +x /scripts/build_wasm.sh
+
+# Set the main command to execute the build script
+WORKDIR /build
+CMD ["/scripts/build_wasm.sh"]